Method for providing a piece of a film of a magnetoelastic material with an enchanced bending stiffness, product obtained by the method and sensor

ABSTRACT

A method for providing a piece of a film of a magnetoelastic material having an initial bending stiffness with an enhanced bending stiffness in a first direction. According to the method, the piece is provided with at least one scored line in the first direction of the piece. Furthermore, the piece is bent along at least one of the at least one scored lines so as to provide the piece with a lasting bend in a direction transverse to the first direction, whereby an enhanced bending stiffness is provided in the first direction of the piece. Also, a product obtained by the method, a sensor and an absorbent structure and an absorbent article including the sensor.

PRIORITY

This application is a national stage application of PCT/SE2006/000675,filed on 8 Jun. 2006.

TECHNICAL FIELD

The present disclosure relates to a method for providing a piece of afilm of a magnetoelastic material having an initial bending stiffnesswith an enhanced bending stiffness in a first direction. In addition,the present disclosure relates to a product comprising a piece of a filmof a magnetoelastic material, which product is obtained by means of themethod. The present disclosure relates also to a sensor comprising apiece of a film of a magnetoelastic material, which piece has an initialbending stiffness in a first direction. Furthermore, the presentdisclosure relates to an absorbent structure and an absorbent articlecomprising the sensor according to the disclosure as well as a sensoringabsorbent system comprising the absorbent structure according to thedisclosure.

BACKGROUND

There are many different types of absorbent articles, such as diapers,diapers of pant type, incontinence garments, sanitary napkins, bedprotectors, wipes, towels, tissues, tampon-like products and wound orsore dressings, known today for absorption, retention and isolation ofbody wastes, such as urine, faeces and blood. Some of the known suchabsorbent articles comprise a sensor which responds to an event, such asurination or defecation, after absorption onto or into the absorbentarticle. The response may, for example, be a signal after the event hasoccurred and may be based on measurement of, for example, wetness, abiological analyte and/or a chemical analyte. The signal of an eventenables the user, parent, care taker, nursing personnel, etc. todetermine with ease that an event has occurred. One type of sensor thatis utilized in some absorbent articles is the magnetoelastic sensor.Magnetoelastic sensors have been described by Grimes et al. (BiomedicalMicrodevices, 2:51-60, 1999). A magnetoelastic sensor comprises a piece,typically a strip, of a magnetoelastic material. Materials that aresuitable to utilize as the magnetoelastic material in a magnetoelasticsensor are materials with a non-zero magnetostriction and a highmagnetoelastic coupling such as, for example, iron-nickel alloys, rareearth metals, ferrites, e.g. spinel type ferrites (Fe₃O₄, MnFe₂O₄),silicon-iron alloys, many other different alloys and mixtures thereof.Soft magnetoelastic materials, alloys and mixtures thereof as well asamorphous magnetoelastic materials, alloys and mixtures thereof may beutilized. Examples of amorphous magnetoelastic alloys are metglases suchas Fe₄₀Ni₃₈Mo₄B₁₈, e.g. Metglas 2826MB™ (Honeywell Amorphous Metals,Pittsburgh, Pa., USA), (FeCo)₈₀B₂₀, (CoNi)₈₀B₂₀ and (FeNi)₈₀B₂₀.

The term “magnetostriction” refers to a phenomenon whereby a materialwill change dimensions in the presence of an external magnetic field.The size of the dimensional change depends on the magnetization in thematerial and, of course, on the material properties. The phenomenon ofmagnetostriction is due to the interaction between the atomic magneticmoments in the material.

The term “a high magnetoelastic coupling” refers to the fact that amaterial having a high magnetoelastic coupling efficiently convertsmagnetic energy into mechanical elastic energy and vice versa. When amaterial that may convert magnetic energy into mechanical elastic energyis excited by a time varying magnetic field, elastic waves mechanicallydeform the material, which has a mechanical resonant frequency inverselyproportional to its length. If the material also is magnetostrictive, itgenerates a magnetic flux when the material is mechanically deformed,which magnetic flux extends remotely and that may be detected by apick-up coil.

Furthermore, a magnetoelastic material of a magnetoelastic sensor storesmagnetic energy in a magnetoelastic mode when excited by an externalmagnetic field. When the magnetic field is switched off, themagnetoelastic material shows damped oscillation with a specificfrequency denoted as the magnetoacoustic resonant frequency. Theseoscillations give rise to a magnetic flux that varies in time, which canbe remotely detected by a pick-up coil. If a pulsed magnetic field suchas, for example, a pulsed sine wave magnetic field is applied to themagnetoelastic material, it will be possible to detect a characteristicresonant frequency, i.e. the magnetoacoustic effect, between themagnetic pulses. The magnetoacoustic resonant frequency is inverselyproportional to the length of the piece of magnetoelastic material.Changes in the magnetoacoustic resonant frequency may be monitored so asto measure or detect multiple environmental parameters.

WO 2004/021944 describes a disposable sensoring absorbent structurecomprising at least one absorbent layer and at least one sensing devicecomprising a magnetoelastic film. The sensoring absorbent structure maybe comprised in an absorbent article such as, for example, a diaper, adiaper of pant type, an incontinence protector, a sanitary napkin or abed protector. In one embodiment the sensing device is intended to beutilized for detection of wetness. The magnetoelastic film of thesensing device is then coated with a wetness sensitive polymer whichinteracts with wetness, e.g. moisture, a liquid or humidity. The wetnesssensitive polymer interacts with wetness, such as urine, throughabsorption or adsorption, whereby the mass of the sensing device ischanged. This change in mass will either increase or decrease themagnetoacoustic resonant frequency of the magnetoelastic film. Thus, themass change is measurable and correlates to the amount of wetnessinteracting with the wetness sensitive polymer. In another embodiment,the magnetoelastic film of the sensing device is coated directly orindirectly with at least one detector molecule adapted to detect atleast one target biological and/or chemical analyte in body waste, bodyexudates or the user's/wearer's skin. WO 2004/021944 is hereinincorporated by reference in its entirety.

It is known to utilize magnetoelastic elements within many othertechnical fields than absorbent articles. For example, it is known toutilize magnetoelastic elements in connection with position sensors,identification markers and as anti-theft tags or electronic articlesurveillance (EAS) tags.

Magnetoelastic materials that may be utilized as the magnetoelasticmaterial in, for example, a magnetoelastic sensor are typically producedas continuous ribbons. However, such ribbons reveal typically alongitudinal curvature or are prone to curve in the longitudinaldirection. The longitudinal curvature, or the tendency to curve in thelongitudinal direction, may be production-inherent and/or may beprovided due to that the ribbon is stored in a rolled form. For example,amorphous ferromagnetic metals are typically produced by rapidsolidification from a melt as continuous ribbons. In such ribbons aproduction-inherent longitudinal curvature may be seen originating fromthermally induced mechanical stresses during rapid solidification.

The fact that the ribbons of magnetoelastic material, which may beutilized for producing magnetoelastic sensors, typically present alongitudinal curvature or are prone to curve in the longitudinaldirection is a common problem. Strips of such ribbons of magnetoelasticmaterial are typically used in magnetoelastic sensors. If a ribbon of amagnetoelastic material reveals a longitudinal curvature or is prone tocurve in the longitudinal direction, a strip cut from the ribbon willalso reveal a longitudinal curvature or will also be prone to curve inthe longitudinal direction. Usually, a magnetoelastic sensor isencapsulated or packaged in an encapsulation, a package, a housing orsimilar device. However, if a strip of a magnetoelastic materialutilized in a magnetoelastic sensor reveals a longitudinal curvature oris prone to curve in the longitudinal direction, an encapsulation musthave a relatively large height to accommodate the magnetoelastic sensorwithout inhibiting the oscillations of the sensor. If the magnetoelasticsensor during vibration touches the encapsulation, the magnetoacousticresonance frequency of the sensor may be disturbed or damped. Forexample, in the field of absorbent articles it is of discretion reasonsimportant that the encapsulation is as thin as possible. Thus, the factthat ribbons of a magnetoelastic material, which may be utilized forproducing magnetoelastic sensors, typically reveal a longitudinalcurvature or are prone to curve in the longitudinal direction causesproblems with respect to the design of encapsulations. Disturbance ofthe oscillations of an encapsulated magnetoelastic sensor is a commonproblem.

Furthermore, it is common to enhance the magnetostrictive effect of themagnetoelastic material of a magnetoelastic sensor by including amagnetic bias field. For example, the magnetic bias field may begenerated by a biasing element such as a permanent magnet or a permanentmagnet film positioned in proximity to the magnetoelastic material.However, the magnetoelastic material and the biasing element exhibittypically a magnetic attraction for one another. Thereby, if themagnetoelastic material reveals a longitudinal curvature or is prone tocurve in the longitudinal direction and if a biasing element ispositioned in proximity to the magnetoelastic material, there is a riskthat the magnetoelastic material will be drawn into contact with thebiasing element and/or, if encapsulated, into contact with theencapsulation. Then the oscillations of the magnetoelastic material willbe disturbed or damped.

A longitudinal curvature of a ribbon of a magnetoelastic material, or atendency of a ribbon of a magnetoelastic material to curve in thelongitudinal direction, may be counteracted and removed by enhancing thelongitudinal bending stiffness of the ribbon. One known way of enhancingthe longitudinal bending stiffness of a ribbon of a magnetoelasticmaterial is to provide the ribbon with a transverse curvature. This isdescribed in, for example, U.S. Pat. No. 5,676,767. In the methodaccording to U.S. Pat. No. 5,676,767, a curling fixture is provided inan oven for the purpose of giving a transverse curvature to a ribbon ofa magnetoelastic material. The ribbon is drawn longitudinally throughthe fixture and the fixture has a curl surface, which proceeding in adirection transverse to the longitudinal axis of the ribbon rises andthe falls. The heating applied to the ribbon during its passage throughthe fixture causes the ribbon to conform itself to the curl surface,thereby providing the ribbon with a transverse curvature. The transversecurvature enhances the longitudinal bending stiffness of the ribbon andcounteracts any longitudinal curvature or tendency to curve in thelongitudinal direction. Thereby, the transverse curvature reduces theabove mentioned problems with disturbance or dampening of theoscillations of the magnetoelastic material and the above mentionedproblems with the encapsulation design. However, this method requiresthat a heat treatment is applied to the magnetoelastic material in orderto enhance the longitudinal bending stiffness. In addition, this methodrequires the use of a fixture and that the magnetoelastic material isdrawn through the fixture. Furthermore, when a magnetoelastic sensorcoated with a polymer such as, for example, a wetness sensitive polymer,is to be produced, this method requires an extra process step before thepolymer may be coated on the magnetoelastic material.

OBJECTS AND SUMMARY

One object is to provide an improved method for providing a piece of afilm of a magnetoelastic material having an initial bending stiffnesswith an enhanced bending stiffness in a first direction.

This object is achieved in accordance with a method that comprises thesteps of:

-   -   providing said piece with at least one scored line in said first        direction of said piece, and    -   bending said piece along at least one of said at least one        scored lines so as to provide said piece with a lasting bend in        a direction transverse to said first direction, whereby an        enhanced bending stiffness is provided in said first direction        of said piece.

In a further aspect, there is provided a product comprising a piece of afilm of a magnetoelastic material, which product is produced by theabove method.

Another object is to provide an improved sensor comprising a piece of afilm of a magnetoelastic material, which piece has an initial bendingstiffness in a first direction. This object is achieved in accordancewith a piece that is provided with at least one scored line in a firstdirection of said piece and that said piece is bent along at least oneof said at least one scored lines such that said piece is provided witha lasting bend in a direction transverse to said first direction,whereby an enhanced bending stiffness is provided in said firstdirection of said piece.

Still other objects and features of the present disclosure will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the disclosure. Itshould be further understood that the drawings are not necessarily drawnto scale and that, unless otherwise indicated, they are merely intendedto conceptually illustrate the structures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters denote similarelements throughout the several views:

FIG. 1 a shows a schematic perspective view of a film of amagnetoelastic material that may be utilized as the magnetoelasticmaterial in a magnetoelastic sensor;

FIG. 1 b shows a schematic perspective view of one example of a striphaving a longitudinal curvature, which strip has been separated from theribbon shown in FIG. 1 a without further processing of the ribbon beforethe separation;

FIG. 2 a shows a schematic perspective view of a strip after an initialstep of a first embodiment of the method according to the disclosure;

FIG. 2 b shows a schematic cross-sectional view of the strip shown inFIG. 2 a;

FIG. 2 c shows a schematic perspective view of the strip shown in FIGS.2 a and 2 b after a bending step of a first embodiment of the methodaccording to the disclosure has been applied to the strip;

FIG. 2 d shows a schematic cross-sectional view of the strip shown inFIG. 2 c;

FIGS. 2 e-2 f show schematic cross-sectional views of the strip shown inFIGS. 2 a and 2 b after variants of the bending step of a firstembodiment of the method according to the disclosure have been appliedto the strip;

FIG. 2 g shows a schematic cross-sectional view of a strip after asecond embodiment of the method according to the disclosure has beenapplied to the strip;

FIGS. 2 h-2 k show schematic cross-sectional views of a strip aftervariants of a third embodiment of the method according to the disclosurehave been applied to the strip;

FIG. 3 a shows a schematic perspective view of a first embodiment of asensor according to the disclosure;

FIGS. 3 b-3 c show schematic cross-sectional views of variants of thefirst embodiment of the sensor according to the disclosure;

FIG. 3 d shows a schematic cross-sectional view of a second embodimentof the sensor according to the disclosure;

FIGS. 3 e-3 f show schematic cross-sectional views of variants of athird embodiment of the sensor according to the disclosure, and

FIG. 4 shows schematically one non-limiting example of an absorbentarticle comprising a sensor according to the disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 a shows a schematic perspective view of a film 1 of amagnetoelastic material that may be utilized as the magnetoelasticmaterial in, for example, a magnetoelastic sensor. The film 1 of amagnetoelastic material shown in FIG. 1 a is provided in the form of aribbon 2 having a transverse direction x and a longitudinal direction y.The ribbon 2 is stored in the form of a roll 3. The ribbon 2 may be seenas being constituted by a number of pieces having the shape of strips 4in the longitudinal direction, which strips 4 are not yet separated ormarked. The boundaries of the respective strips 4 are indicated bydashed lines in FIG. 1 a. Furthermore, the ribbon 2 reveals alongitudinal curvature, which is schematically shown in FIG. 1 a. Asabove described, a ribbon of a magnetoelastic material that may beutilized as the magnetoelastic material in, for example, amagnetoelastic sensor reveals typically a longitudinal curvature or isprone to curve in the longitudinal direction. The longitudinalcurvature, or the tendency to curve in the longitudinal direction, maybe production-inherent and/or may be provided due to that the ribbon isstored in a rolled form. The term “longitudinal curvature” is hereinintended to mean a curvature which has an extension in the longitudinaldirection of a film of a magnetoelastic material. Thus, a ribbon of afilm of a magnetoelastic material that reveals a longitudinal curvaturereveals a curvature in the longitudinal direction of the ribbon, i.e.the ribbon is curved in the longitudinal direction. A strip that isseparated from a ribbon, which reveals a longitudinal curvature or isprone to curve in the longitudinal direction, will also reveal alongitudinal curvature or be prone to curve in the longitudinaldirection if no further processing of the ribbon is performed before theseparation. FIG. 1 b shows a schematic perspective view of one exampleof one of the strips 4 constituting the ribbon 2 after it has beenseparated from the ribbon 2. The strip 4 shown in FIG. 1 b has beenseparated from the ribbon 2 shown in FIG. 1 a without further processingof the ribbon 2 before the separation. The strip 4 has a transversedirection x and a longitudinal direction y.

The present disclosure provides a method for providing a piece of a filmof a magnetoelastic material having an initial or inherent bendingstiffness with an enhanced bending stiffness in a first direction. Themethod according to an embodiment the disclosure comprises the steps of:

-   -   providing the piece with at least one scored line in the first        direction of the piece, and    -   bending the piece along at least one of the at least one scored        lines so as to provide the piece with a lasting bend in a        direction transverse to the first direction, whereby an enhanced        bending stiffness is provided in the first direction of the        piece.

The magnetoelastic material of the piece, to which the method accordingto the disclosure may be applied, may be any known magnetoelasticmaterial. For example, it may be applied to any magnetoelastic materialwith a non-zero magnetostriction and a high magnetoelastic coupling.Examples of such magnetoelastic materials are iron-nickel alloys, rareearth metals, ferrites, e.g. spinel type ferrites (Fe₃O₄, MnFe₂O₄),silicon-iron alloys, many other different alloys and mixtures thereof.Furthermore, the method according to the disclosure may be applied to,for example, soft magnetoelastic materials, alloys and mixtures thereofas well as amorphous magnetoelastic materials, alloys and mixturesthereof. Examples of amorphous magnetoelastic alloys are metglases suchas Fe₄₀Ni₃₈Mo₄B₁₈, e.g. Metglas 2826MB™ (Honeywell Amorphous Metals,Pittsburgh, Pa., USA), (FeCo)₈₀B₂₀, (CoNi)₈₀B₂₀ and (FeNi)₈₀B₂₀.

Furthermore, the method according to the disclosure may be applied to apiece having the shape of a strip, a ribbon or any other shape. Thepiece, to which the method according to the disclosure is applied, maybe an integral part of a ribbon or may be a separate piece. Furthermore,the method according to the disclosure may be applied to a piece beingan integral part of a ribbon stored in a rolled form or any other form.For example, the method according to the disclosure may be applied tothe ribbon 2 shown in FIG. 1 a, to one of the strips 4 being an integralpart of the ribbon 2 shown in FIG. 1 a or to the strip 4 shown in FIG. 1b.

Different embodiments of the method according to the disclosure will nowbe described when applied to the piece 4 of a film 1 of a magnetoelasticmaterial having the shape of a strip shown in FIG. 1 b for providing thestrip 4 with an enhanced bending stiffness in the longitudinaldirection, i.e. in a first direction.

In an initial step of a first embodiment of the method according to thedisclosure, the strip 4 is provided with a scored line/notch/slit 5 inthe longitudinal direction on a first side 6 of the strip 4. Thus, thestrip 4 is then provided with a scored line 5 extending in thelongitudinal direction of the strip 4. In the first embodiment thescored line 5 is provided essentially centralized on the strip 4, i.e.it is provided essentially in the middle of the strip 4. FIG. 2 a showsa schematic perspective view of the strip 4 after the initial step ofproviding the strip 4 with a scored line 5. FIG. 2 b shows a schematiccross-sectional view of the strip 4 shown in FIG. 2 a.

The depth of the scored line 5 is less than the thickness of the film 1of the strip 4, i.e. the scored line 5 does not extend through thecomplete thickness of the film 1 of the strip 4. The thickness of thefilm 1 of a magnetoelastic material that the method according to thedisclosure may be applied to is typically about 0.01-1000 μm, such as0.01-200 μm, 5-100 μm or 0.01-100 μm. The depth of the scored line 5 maybe, for example, 1-40% of the film thickness, preferably 10-20% of thefilm thickness.

In the first embodiment of the method according to the disclosure, thestrip 4 is provided with the scored line 5 by an etching process. Theutilized etching process may be any known etching process that issuitable for providing a scored line 5 in a film 1 of a magnetoelasticmaterial. For example, the etching process may be a chemical process, anelectrochemical process or an ion-beam process. Furthermore, aphotoetching process combining photolithography with the etching processmay also be utilized.

One non-limiting example of an etching process that may be utilized inthe first embodiment of the present disclosure will now described inbroad outline. In this example the strip 4 is coated on the first side 6with a photoresist in a first step. A second side 7, i.e. the sideopposite the first side 6, of the strip 4 is then also provided with asuitable cover for protection during the etching process. In a secondstep the photoresist is exposed to light through a mask. Depending onwhether a positive or negative photoresist is utilized, the mask isdesigned either such that those parts of the photoresist are exposed tolight that cover parts of the strip 4 where the scored line 5 is to becreated, or such that those parts of the photoresist are exposed tolight that do not cover parts of the strip 4 where the scored line 5 isto be created. In a third step those parts of the photoresist areremoved that cover the parts of the strip 4 where the scored line 5 isto be created. Thereafter the strip 4 is etched in a fourth step bymeans of a suitable etchant such as, for example, an acid or ferricchloride. The remaining photoresist on the first side 6 and the cover onthe second side 7 serve then as barriers against the etchant. Thereby,the strip 4 is exposed to the etchant only in those parts where thescored line 5 is to be produced. After the etching step, the remainingphotoresist is removed.

The above described non-limiting example of an etching process and otheretching processes suitable to utilize in the method according to thedisclosure are well-known for persons skilled in the art and aretherefore not further explained.

In a subsequent step of the first embodiment, the strip 4 being providedwith one scored line 5 is bent along the scored line 5 so as to providethe strip 4 with a lasting bend in the transverse direction of the strip4, i.e. in a direction transverse to the first direction. The fact thatthe strip 4 is provided with a lasting bend in the transverse directionimplies that the strip 4 is provided with a cross-sectional shapedeviating from a planar cross-sectional shape. A lasting bend orpermanent bend is provided by means of the bending step due to the factthat the bending is performed such that the magnetoelastic material isat least partially plastically deformed at a bottom 8 of the scored line5 along which the strip 4 is bent.

In the first embodiment, the strip 4 is bent along the scored line 5 soas to provide the strip 4 with a lasting bend being angular. After thebending step, the cross-section of the strip 4 is thereby angular. Thus,the bending of the strip 4 is in the first embodiment performed suchthat an angle α is enclosed. The bending in the first embodiment may beperformed such that any suitable angle α within the range of 0<α<180° isenclosed. For example, the strip 4 may in the first embodiment be bentso as to provide the strip 4 with a lasting bend enclosing an angle αgreater than 90° (FIGS. 2 c-2 d). The strip 4 may, for example, be bentsuch that α is 160°≦α<180°. Preferably a is 170°≦α<180°. However, thestrip 4 may in the first embodiment also be bent so as to provide thestrip 4 with a lasting essentially right-angular bend (FIG. 2 e) or alasting bend enclosing an angle α less than 90° such as a lastingV-shaped bend (FIG. 2 f). FIG. 2 c shows a schematic perspective view ofthe strip 4 shown in FIGS. 2 a and 2 b after it has been provided with alasting bend enclosing an angle α greater than 90° and FIG. 2 d shows aschematic cross-sectional view of the strip 4 shown in FIG. 2 c. FIG. 2e shows a schematic cross-sectional view of the strip 4 shown in FIGS. 2a and 2 b after it has been provided with a lasting essentiallyright-angular bend and FIG. 2 f shows a schematic cross-sectional viewof the strip 4 shown in FIGS. 2 a and 2 b after it has been providedwith a lasting bend enclosing an angle less than 90°.

Furthermore, the strip 4 may be bent along the scored line 5 either suchthat it is bent towards or away from the scored line 5.

Since the strip 4 is provided with a lasting bend in the transversedirection of the strip 4, an enhanced bending stiffness is provided inthe longitudinal direction of the strip 4. The enhanced bendingstiffness achieved will counteract and/or remove any curvature of thestrip 4 in the longitudinal direction, or any tendency to curve in thelongitudinal direction, which may be production-inherent and/or provideddue to that films 1 of magnetoelastic materials are stored in a rolledform.

Preferably, the bending is performed by means of a mould, or in a mould,such that a controlled bending of the strip 4 is achieved. For example,the mould utilized may comprise a bending surface, which has such ashape such that the strip 4 may be bent along the scored line 5 and maybe given a desired bend in the transverse direction when it is pressedat least partially against the bending surface. The strip 4 may bepressed against the bending surface by means of any suitable means. Forexample, it may be pressed against the bending surface by means of asecond mould having a second bending surface. The strip 4 is thenpositioned between the two bending surfaces of the two moulds during thebending. The second bending surface has then such a shape such that italso contributes to bending the strip 4 along the scored line 5 and togiving the strip 4 a desired bend in the transverse direction.Furthermore, instead of utilizing one or more moulds for the bending,the strip 4 may be bent between two rolls having bending surfaces suchthat a desired bending is achieved.

A second embodiment of the method according to the disclosurecorresponds to the first embodiment except for that the scored line 5 isnot provided such that it is centralized on the strip 4. Instead thescored line 5 is provided on the strip 4 such that it is positioned at ashorter distance to one of the longitudinal side edges of the strip 4than to the other of the longitudinal side edges. The bending step inthe second embodiment is performed such that any suitable angular bendis achieved, i.e. such that any suitable angle α within the range of0<α<180° is enclosed. For example, the bending step in the secondembodiment may be performed so as to provide the strip 4 with a lastingbend enclosing an angle α greater than 90° (not shown). The strip 4 may,for example, be bent such that α is 160°≦α<180°. Preferably α is170°≦α<180°. However, the strip 4 may in the second embodiment also bebent so as to provide the strip 4 with a lasting essentiallyright-angular bend (FIG. 2 g) or a lasting bend enclosing an angle αless than 90° (not shown). Furthermore, the scored line 5 may in thesecond embodiment be provided at such a position on the strip 4 and thestrip 4 may be bent so as to provide the strip 4 with a lasting L-shapedbend. FIG. 2 g shows a schematic cross-sectional view of a strip 4 beingprovided with an essentially right-angular bend, which is L-shaped.

A third embodiment of the method according to the present disclosurecorresponds to the first embodiment except for that the first side 6 isprovided with more than one scored line 5, i.e. it is provided with twoor more scored lines 5 extending in the longitudinal direction of thestrip 4. The scored lines 5 may in the third embodiment be provided atany suitable positions and at any distance from each other or from anyof the longitudinal side edges, so as to be positioned such that adesired shape of the bend may be achieved when the strip 4 is bent alongthe scored lines 5 in the bending step.

For example, the strip 4 may in the third embodiment be provided withtwo scored lines 5 and the strip 4 may be bent along the two scoredlines 5 in the bending step such that a cup-shaped bend is achieved. Across-sectional view of one example of a strip 4 after such a variant ofthe third embodiment is shown in FIG. 2 h. Another alternative is thatthe strip 4 in the third embodiment is provided with several scoredlines 5 on the first side 6 and that the strip 4 is bent along theseveral scored lines 5 such that a curve-shaped bend is achieved. Forexample, a bend may then be achieved that forms a part of a circle orthat is U-shaped. A cross-sectional view of one example of a strip 4after such a variant of the third embodiment is shown in FIG. 2 i. Thus,by providing several scored lines 5 on the first side 6 of the strip 4and bending the strip 4 along the several scored lines 5 it is possibleto provide the strip 4 with a transverse curvature. The term “transversecurvature” is herein intended to mean a curvature which has an extensionin the transverse direction of a film 1 of a magnetoelastic material.Thus, a strip 4 of a film 1 of a magnetoelastic material that reveals atransverse curvature reveals a curvature in the transverse direction ofthe strip 4, i.e. the strip 4 is curved in the transverse direction.Furthermore, the strip 4 may in the third embodiment be provided withseveral scored lines 5 on the first side 6 and be bent along the severalscored lines 5 such that an S-shaped bend (FIG. 2 j) or a wave-shapedbend (FIG. 2 k) is achieved. Cross-sectional views of examples a strip 4after such variants of the third embodiment are shown in FIG. 2 j andFIG. 2 k. The scored lines 5 are omitted in FIGS. 2 j and 2 k forclarity reasons.

A fourth embodiment of the method according to the disclosurecorresponds to any of the above described embodiments except for thatone or more scored lines 5 is/are provided on each side 6, 7 of thestrip 4, i.e. at least one scored line 5 is provided on the first side 6and at least one scored line 5 is provided on the second side 7.

As may be realized from the above, any suitable number of scored lines 5may be provided on the strip 4, at any suitable positions on the strip4, in the method according to embodiments of the disclosure so as toenable bending of the strip 4 such that a shape of the lasting bend isachieved that enhances the longitudinal bending stiffness of the strip4. Furthermore, an active bending is not required along all providedscored lines 5 in the method according to the disclosure, i.e. scoredlines 5 may be provided along which the strip 4 is not bent.

Even if different embodiments of the method according to the disclosurehave been described when applied to a piece of a film 1 of amagnetoelastic material having the shape of a strip and being a separatepiece, the described embodiments may also be applied to a piece of afilm 1 of a magnetoelastic material having any other shape or to a piecebeing an integral part of, for example, a ribbon. Thus, any of the abovedescribed embodiments of the method according to the disclosure may, forexample, be applied to one of the strips 4 constituting the ribbon 2shown in FIG. 1 a. Then the strip 4, to which the method is applied, isoptionally separated from the ribbon 2 between the step of providing oneor more scored lines 5 on the strip 4 and the step of bending. Forexample, the strip 4 may then be separated from the ribbon 2 in a stepof cutting following the step of providing one or more scored lines 5 onthe strip 4. Alternatively, if etching is utilized for providing one ormore scored lines 5 on the strip 4, the step of etching may thenoptionally be performed such that the strip 4 not only is provided withone or more scored lines 5 in the etching process but also such that thestrip 4 is separated from the ribbon 2 in the etching process. Then theribbon 2 is etched in the areas where the scored line(s) 5 is/are to becreated and along one or more separation lines, i.e. along one or morelines where the strip 4 is to be separated from the ribbon 2. Along theseparation line(s) the ribbon 2 is etched through such that the strip 4is separated from the ribbon 2.

Furthermore, even if the method according to the disclosure has beendescribed for providing a piece of a film of a magnetoelastic materialwith an enhanced bending stiffness in the longitudinal direction, themethod according to the disclosure may be applied for providing a filmof a magnetoelastic material with an enhanced bending stiffness in anyother desired direction. The scored line(s) 5 is/are then provided inthe direction in which an enhanced bending stiffness is desired. Inaddition, the method according to the disclosure may be applied to apiece of a film of a magnetoelastic material revealing a curvature inany direction or being essentially plane.

Furthermore, the piece of a film of a magnetoelastic material, to whichthe method is applied, may be coated at least partially with a wetnesssensitive polymer on one of the first and second sides 6, 7 or be coateddirectly or indirectly on one of the first and second sides 6, 7 with atleast one detector molecule adapted to detect at least one targetbiological and/or chemical analyte. Then the piece is preferablyprovided with one or more scored lines 5 only on the side 6, 7 that isnot coated with the wetness sensitive polymer or any detectormolecule(s). Furthermore, if etching is utilized for providing one ormore scored lines 5 on the piece, the wetness sensitive polymer or thedetector molecule(s) is/are then provided with a cover for protectionduring the step of etching. Examples of wetness sensitive polymers,detector molecules as well as biological and chemical analytes that thedetector molecules may be adapted to detect are given below.

In variants of any of the above described embodiments of the methodaccording to the disclosure, the piece of a film of a magnetoelasticmaterial is provided with one or more scored lines through scribinginstead of etching.

When any of the above described embodiments of the method according tothe disclosure is applied to a piece of a film of a magnetoelasticmaterial, a product comprising a piece of a film of a magnetoelasticmaterial is obtained. The product may, for example, be utilized as asensor or in a sensor. If the piece of a film of a magnetoelasticmaterial is not coated with any additional layer, such as a layer of awetness sensitive polymer, or any detector molecules, the productobtained when the example, identification markers, position sensors,anti-theft tags or electronic article surveillance (EAS) tags.

Furthermore, the present disclosure provides a sensor comprising a filmof a magnetoelastic material. The sensor according to the disclosure maybe obtained by utilizing the method according to the disclosure or anyother method yielding the same result. FIG. 3 a shows a schematicperspective view of a first embodiment of a sensor 11 according to thedisclosure.

The first embodiment of the sensor 11 according to the disclosurecomprises a strip 4 of a film 1 of a magnetoelastic material. Themagnetoelastic material of the strip 4 may be any known magnetoelasticmaterial. For example, it may be any magnetoelastic material with anon-zero magnetostriction and a high magnetoelastic coupling. Examplesof such magnetoelastic materials are iron-nickel alloys, rare earthmetals, ferrites, e.g. spinel type ferrites (Fe₃O₄, MnFe₂O₄),silicon-iron alloys, many other different alloys and mixtures thereof.Furthermore, the magnetoelastic material may be any material selectedfrom the group of soft magnetoelastic materials, alloys and mixturesthereof as well as amorphous magnetoelastic materials, alloys andmixtures thereof. Examples of amorphous magnetoelastic alloys aremetglases such as Fe₄₀Ni₃₈Mo₄B₁₈, e.g. Metglas 2826MB™ (HoneywellAmorphous Metals, Pittsburgh, Pa., USA), (FeCo)₈₀B₂₀, (CoNi)₈₀B₂₀ and(FeNi)₈₀B₂₀. The thickness of the film 1 of a magnetoelastic material istypically about 0.01-1000 μm, such as 0.01-200 μm, 5-100 μm or 0.01-100μm. The film 1 of a magnetoelastic material has an initial or inherentbending stiffness.

The strip 4 shown in FIG. 3 a is provided with a scored line/notch/slit5 in the longitudinal direction, i.e. in a first direction, on a firstside 6. Thus, the strip 4 is provided with a scored line 5 extending inthe longitudinal direction. The scored line 5 is provided essentiallycentralized on the strip 4, i.e. it is provided essentially in themiddle of the strip 4. The depth of the scored line 5 is less than thethickness of the film 1 of the strip 4, i.e. the scored line 5 does notextend through the complete thickness of the film 1 of the strip 4. Thedepth of the scored line 5 may be, for example, 1-40% of the filmthickness, preferably 10-20% of the film thickness. Furthermore, thestrip 4 is bent along the scored line 5 such that the strip 4 isprovided with a lasting or permanent bend in the transverse direction ofthe strip 4, i.e. in a direction transverse to the first direction. Thebend is a lasting or permanent bend due to that the magnetoelasticmaterial is at least partially plastically deformed at a bottom 8 of thescored line 5 along which the strip 4 is bent. The fact that the strip 4is provided with a bend in the transverse direction implies that thestrip 4 is provided with a cross-sectional shape deviating from a planarcross-sectional shape.

Furthermore, the bend of the strip 4 shown in FIG. 3 a is angular,whereby the cross-section of the strip 4 is angular. More specifically,the bend of the strip 4 shown in FIG. 3 a encloses an angle α that isgreater than 90°.

Since the strip 4 is provided with a lasting bend in the transversedirection of the strip 4, an enhanced bending stiffness, i.e. a bendingstiffness that is greater than an initial or inherent bending stiffnessof the strip 4, is provided in the longitudinal direction of the strip4. The enhanced bending stiffness achieved will counteract and/or removeany curvature of the strip 4 in the longitudinal direction, or anytendency to curve in the longitudinal direction, which may beproduction-inherent and/or provided due to that films 1 ofmagnetoelastic materials are stored in rolled forms.

Furthermore, the strip 4 shown in FIG. 3 a is coated at least partiallywith a layer 12 of wetness sensitive polymer on a second side 7, i.e.the side opposite the first side 6, which wetness sensitive polymer isselected from the group consisting of linear and hydrophilic polymers orchemically/physically cross-linked swellable polymer gels based onpolyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide andco-polymers thereof, polyurethane, polyamides, starch and derivativesthereof, cellulose and derivative thereof, polysaccharides, proteins,polyacrylonitrile, polyethylene imine, acrylate based polymers, andmixtures thereof.

The wetness sensitive polymer may interact with wetness such as aliquid, humidity or moisture through, for example, absorption oradsorption. When the wetness sensitive polymer interacts with wetness,the mass of the first embodiment of the sensor 11 is changed resultingin a change of the resonant frequency, e.g. the magnetoacoustic resonantfrequency, of the sensor 11. The change of the magnetoacoustic resonantfrequency is detectable and correlates to the amount of wetness that thewetness sensitive polymer has interacted with, i.e. it correlates, forexample, to the amount of wetness absorbed or adsorbed by the wetnesssensitive polymer. Thus, the sensor 11 shown in FIG. 3 a may be utilizedas a wetness sensor. For example, it may be utilized for detecting bodydischarges such as body fluids, body waste or body exudates, i.e. urine,faeces, blood, menstruation blood, fluid matters from wounds and sores,rinsing fluid and saliva.

Even if the bend shown in FIG. 3 a is shown as enclosing a specificangle α, the bend of the strip 4 of the sensor 11 according to the firstembodiment may enclose any suitable angle α within the range of0°<α<180°. Thereby the bend of a strip 4 of a sensor 11 according to thefirst embodiment may enclose an angle α that is greater than 90° (FIG. 3a). The strip 4 may, for example, be bent such that α is 160°≦α<180°.Preferably α is 170°≦α<180°. However, the bend of the strip 4 of thesensor 11 according to the first embodiment may also enclose anessentially right angle, whereby the bend is right-angular (FIG. 3 b),or an angle α that is less than 90° (FIG. 3 c). FIG. 3 b shows aschematic cross-sectional view of a sensor 11 according to the firstembodiment in which the strip 4 is provided with a right-angular bend.FIG. 3 c shows a schematic cross-sectional view of a sensor 11 accordingto the first embodiment in which the strip 4 is provided with a bendenclosing an angle α that is less than 90°.

Furthermore, the strip 4 of the first embodiment of the sensor 11according to the disclosure may be bent along the scored line 5 eithersuch that it is bent towards or away from the scored line 5.

A second embodiment of the sensor 11 according to the disclosurecorresponds to the first embodiment of the sensor 11 except for the factthat the scored line 5 is not provided such that it is centralized onthe strip 4. Instead the scored line 5 is provided on the strip 4 suchthat it is positioned at a shorter distance to one of the longitudinalside edges of the strip 4 than to the other of the longitudinal sideedges. The lasting bend of the strip 4 of the sensor 11 according to thesecond embodiment is angular and may enclose any suitable angle α withinthe range of 0°<α<180°. For example, a strip 4 of a sensor 11 accordingto the second embodiment may be provided with a lasting bend enclosingan angle α more than 90° (not shown). The strip 4 may, for example, bebent such that α is 160°≦α<180°. Preferably α is 170°≦α<180°. However, astrip 4 of a sensor 11 according to the second embodiment may also beprovided with a lasting essentially right-angular bend (FIG. 3 d) or alasting bend enclosing an angle α less than 90° (not shown).Furthermore, the scored line 5 may be provided at such a position on thestrip 4 and the strip 4 may be bent such that the strip 4 is providedwith a lasting L-shaped bend. FIG. 3 d shows a schematic cross-sectionalview of a second embodiment of a sensor 11 according to the disclosure,in which the strip 4 is provided with a lasting L-shaped bend.

A third embodiment of the sensor 11 according to the disclosurecorresponds to the first embodiment of the sensor 11 except for the factthat the first side 6 of the strip 4 is provided with more than onescored line 5, i.e. it is provided with two or more scored lines 5extending in the longitudinal direction of the strip 4. The scored lines5 may in the third embodiment be provided at any suitable positions andat any distance from each other or from any of the longitudinal sideedges. The strip 4 is bent along the scored lines 5 in the thirdembodiment such that the strip 4 is provided with a lasting bend havingany suitable shape. For example, the strip 4 may in the third embodimentof the sensor 11 be provided with two scored lines 5 and the strip 4 maybe bent along the two scored lines 5 such that the strip 4 is providedwith a cup-shaped bend (not shown). Another alternative is that thestrip 4 in the third embodiment of the sensor 11 is provided withseveral scored lines 5 on the first side 6 and that the strip 4 is bentalong the several scored lines 5 such that the strip 4 is provided witha curve-shaped bend. For example, the bend may then form a part of acircle or be U-shaped. Thus, the strip 4 may in the third embodiment ofthe sensor 11 be provided with a transverse curvature. A cross-sectionalview of one example of a sensor 11 according to the third embodiment, inwhich the strip 4 is provided with a curve-shaped bend, is shown in FIG.3 e. Furthermore, the strip 4 may in the third embodiment of the sensor11 according to the disclosure be provided with several scored lines 5on the first side 6 and be bent along the several scored lines 5 suchthat an S-shaped or wave-shaped bend is provided. A schematiccross-sectional view of one example of a sensor 11 according to thethird embodiment, in which the strip 4 is provided with an S-shapedbend, is shown in FIG. 3 f. The scored lines 5 are omitted in FIG. 3 ffor clarity reasons.

A fourth embodiment of the sensor 11 according to the disclosurecorresponds to any of the above described embodiments except for thefact that one or more scored lines 5 is/are provided on each side 6, 7of the strip 4, i.e. at least one scored line 5 is provided on the firstside 6 and at least one scored line 5 is provided on the second side 7.

In a variant (not shown) of any of the above described embodiments ofthe sensor 11 according to the disclosure, the strip 4 is, instead ofbeing coated with a layer 12 of a wetness sensitive polymer, coateddirectly or indirectly, i.e. with other layers such as suitable couplinglayers in-between, on one of the first and second sides 6, 7 with atleast one detector molecule adapted to detect at least one targetbiological and/or chemical analyte.

The detector molecule may in one embodiment be adapted to detect abiological or chemical analyte selected from the group consisting of anenzyme or a sequence of enzymes; an antibody; a nucleic acid, such asDNA or RNA; a protein, such as a soluble protein or a membrane protein;a peptide, such as an oligopeptide or a polypeptide; an organelle; partsof a natural or synthetic cell membrane or capside, such as a bacterialor a mammalian cell membrane, or a virus capside; an intact or partialviable or nonviable bacterial, plant or animal cell; a piece of plant ormammalian tissues or any other biologically derived molecule; a lipid, acarbohydrate; a lectin, and mixtures thereof.

In another embodiment the detector molecule may be adapted to detect abiological or chemical analyte selected from the group consisting ofpathogenic bacteria; non-pathogenic bacteria, e.g. colonic bacteria;viruses; parasites; bacterial toxins; fungi; enzymes; proteins;peptides; mammalian blood cells, such as human white or red blood cells;hormones; mammalian, including human, blood components, such as bloodglucose; urine and its components such as glucose, ketones,urobilinogen, and bilirubin; and mixtures thereof.

The bacteria that the detector molecule may be adapted to detect,pathogenic or not, is selected from the group consisting of Escherichiacoli, Salmonela typhi, Salmonella paratyphi, Salmonella enteriditid,Salmonella thyphimurium, Salmonella heidelberg, Staphylococcus aureus,Shigella sonnei, Shigella flexneri, Shigella boydii, Shigelladysenteriae, Vibrio cholerae, Mycobacterium tuberculosis, Yersinaenterocolitica, Aeromonas hydrophila, Plesmonas shigelloides,Campylobacter jejuni, Campylobacter coli, Bacteroides fragilis,Clostridia septicum, Clostridia perfringens, Clostridia botulinum,Clostridia difficile, and mixtures thereof.

In still another embodiment the detector molecule is adapted to detect achemical compound or chemical analyte such as health markers ornutritional markers. Nutritional markers include markers for e.g.metabolic efficiency, nutrient deficiencies, nutrient absorption ormalabsorption, food and drink intake, food allergies (e.g. to peanuts),food intolerance (e.g. lactose or gluten intolerance), colonic bacteriaecology (e.g. beneficial bacterias such as bifidobacteria andlactobacillus), and total energy balance. Health markers may includechemical analytes such as heavy metals (e.g. lead, mercury, etc.),radioactive substances (e.g. caesium, strontium, uranium, etc.), fats,enzymes, endogenous secretions, protein matter (e.g. blood casts),mucous, and micro-organisms, as described above, that may be related tovarious health issues such as infection, diarrhoea, gastrointestinaldistress of disease, or poisoning. Heavy metals, especially in certaindeveloping countries and in older and/or less affluent areas ofdeveloped countries, are serious health risks. For example, lead andmercury poisoning may occur upon the ingestion of these heavy metalsfrom environmental sources (e.g. from lead paint, unregulated heavyindustries, etc.) and can be fatal. More commonly, low-level poisoningby these and other heavy metals results in retarded intellectual and/orphysical development, especially in children that may occur over a longtime and have lasting effects on the individual. Other examples ofnutritional markers include calcium, vitamins (e.g. thiamine,riboflavin, niacin, biotin, folic acid, pantothenic acid, absorbic acid,vitamin E, etc.), electrolytes (e.g. sodium, potassium, chlorine,bicarbonate, etc.), fats, fatty acids (long and short chain), soaps(e.g. calcium palmitate), amino acids, enzymes (e.g. lactose, amylase,lipase, trypsin, etc.), bile acids and salts thereof, steroids, andcarbohydrates. For example, calcium malabsorption is important in thatit may lead to a long-term bone-mass deficiency.

Suitable detector molecules may include any biorecognition element andare further exemplified by carbohydrates, antibodies or parts thereof,synthetic antibodies or parts thereof, enzymes, lectins, DNA(deoxyribonucleic acid), RNA (ribonucleic acid), cells and/or cellmembranes or any other molecule with a binding capacity for a definedbioanalyte or chemical analyte.

For example, the detector molecules may be wholly or partiallyphysiosorbed onto one of the first and second sides 6, 7 of the strip 4using e.g. a cationic polymer such as polyethylene imine (PEI, from e.g.Sigma-Aldrich), a colloidal suspension such as polybead polystyrene (PS)microspheres (from e.g. Scientific Polymer Products), or a hydrophobicpolymer such as polystyrene (from e.g. Scientific Polymer Products).

It is obvious to a person skilled in the art that any suitable means ofapplying the detector molecule than physiosorption onto one of the firstand second sides 6, 7 of the strip 4 will be appropriate for otherapplications. For example, it may be desirable to chemically bind thedetector molecule, directly or indirectly, to one of the first andsecond sides 6, 7 using any one of a variety of common crosslinkermolecules including, but not limited to, glutaraldehyde,N-hydroxysuccinimide, carbodidimides.

When a detector molecule comprised in a sensor 11 according to thedisclosure detects a biological and/or chemical analyte, the mass of thesensor 11 changes resulting in a change of the magnetoacoustic resonantfrequency of the sensor 11, which is detectable.

In another variant of any of the above described embodiments of thesensor 11 according to the disclosure, the piece of a magnetoelasticmaterial of the sensor 11 is not coated with any additional layer, suchas a layer 12 of a wetness sensitive polymer, or any detector molecules.The sensor 11 may then, for example, be utilized in connection withposition sensors.

As may be realized from the above, a strip 4 of a sensor 11 according tothe present disclosure may be provided with any suitable number ofscored lines 5. Furthermore, the scored line(s) 5 may be provided at anysuitable position(s) on the strip 4 such that a suitable shape of alasting bend is provided. In addition, the strip 4 may be provided withone or more scored lines 5 along which the strip 4 is not bent.

Furthermore, in variants of any of the above described embodiments, thepiece of a film of a magnetoelastic material of the sensor 11 accordingto the disclosure has any other suitable shape than the shape of astrip. For example, the piece of a magnetoelastic material may then havethe shape of a ribbon. In addition, even if the piece of amagnetoelastic material according to the disclosure in the embodimentsdescribed above has been provided with an enhanced bending stiffness inthe longitudinal direction, it may in variants of any of the abovedescribed embodiments be provided with an enhanced bending stiffness inany other direction. The scored line(s) 5 is/are then provided in thedirection in which an enhanced bending stiffness is provided.

As above described, a magnetoelastic material of a magnetoelastic sensorstores magnetic energy in a magnetoelastic mode when excited by anexternal magnetic field. When the magnetic field is switched off, themagnetoelastic material shows damped oscillation with a specificfrequency denoted as the magnetoacoustic resonant frequency. Theseoscillations give rise to a magnetic flux that varies in time, which canbe remotely detected by a pick-up coil. Thus, the magnetoacousticresonant frequency is detectable and thereby also a change of themagnetoacoustic resonant frequency. If a pulsed magnetic field isapplied to a magnetoelastic material, the magnetoacoustic resonantfrequency may be detected between the magnetic pulses. Themagnetoacoustic resonant frequency for e.g. a strip of a magnetoelasticmaterial is inversely proportional to the length of the strip.

For example, a pulsed magnetic field or a pulsed sine wave magneticfield may be applied to the sensor 11 according to embodiments of thedisclosure in order to detect the magnetoacoustic resonant frequency ofthe sensor 11. As mentioned above, the magnetoacoustic resonantfrequency may then be detected between the pulses. The amplitude of thepulsed magnetic field must be large enough to magnetize themagnetoelastic material to a certain amount in order to achieve asufficiently large change in material dimensions. The dimensions of themagnetoelastic material change due to the effect of magnetostriction.The specific magnetic field utilized must be optimised for eachmagnetoelastic material.

The pulse frequencies used may, for example, be about 10-1000 Hz, suchas about 50-700 Hz. The duty cycles of the pulses may, for example, beabout 1-90%, such as about 10-50%. If the magnetic field is a pulsedsine wave field, the sine waves may, for example, be about 50-80 kHz. IfMETGLAS® material from Honeywell is used as the magnetoelastic material,a magnetic field amplitude of the pulsing field may be about 0.05-0.1mT.

An excitation coil may, for example, be utilized for applying a magneticfield to the magnetoelastic material of a sensor 11. A pick-up coil may,for example, be utilized for collecting the produced signal, i.e. themagnetoacoustic effect. The excitation coil and the pick-up coil may belocated in a hand held unit. Furthermore, the excitation coil and thepick-up coil may be located in the same hand held unit or in differenthand held units. In an alternative, the same coil may be utilized asboth excitation coil and pick-up coil, i.e. both for excitation anddetection. WO 2004/021944 is herein incorporated by reference in itsentirety for further details regarding the excitation of themagnetoelastic material, detection of the magnetoacoustic resonantfrequency as well as changes thereof and devices for detection of themagnetoacoustic resonant frequency.

One way of further enhancing the magnetostrictive effect of themagnetoelastic material in the sensor 11 according to the disclosure isto include a magnetic bias field. For example, a magnetic bias field maybe generated by a permanent magnetic film or a permanent magnetpositioned in proximity to the piece of a magnetoelastic material of thesensor 11. When METGLAS® material from Honeywell is used as themagnetoelastic material, a magnetic bias field of about 0.5-1 mT may beutilized.

A sensor 11 may be positioned in contact with or in spaced relation withan absorbent material of an absorbent structure of an absorbent article.For example, a sensor 11 may be comprised in an absorbent structure inan absorbent article, such as a diaper, a diaper of pant type, anincontinence garment, a sanitary napkin, a wipe, a towel, a tissue, abed protector, a wound or sore dressing, a tampon-like product, orsimilar product. In normal use, an absorbent structure in such anabsorbent article serves to absorb, retain and isolate body wastes orbody exudates, e.g. urine, faeces, blood, menstruation blood, fluidmatter from wounds and sores, rinsing fluid and saliva. When a sensor11, in which the piece of a magnetoelastic material is at leastpartially coated with a layer 12 of a wetness sensitive polymer or atleast one detector molecule, is comprised in such an absorbent structureit will enable easy detection of wetness or a biological and/or chemicalanalyte, i.e. it will enable easy detection of that an event such asurination or defecation has occurred. The detection is performed bydetecting a change of the magnetoacoustic resonant frequency of thesensor 11. Thereby the status of the absorbent structure and, thus, ofthe absorbent article may be easily monitored by a user, parent, caretaker, etc.

For example, a sensor 11, in which the piece of a magnetoelasticmaterial is at least partially coated with a layer 12 of a wetnesssensitive polymer or at least one detector molecule, may replace thesensing device disclosed in WO 2004/021944 and thus be comprised in theabsorbent structures and absorbent articles disclosed in WO 2004/021944.Thus, such a sensor 11 may be positioned in different positions in anabsorbent structure in accordance with the positions of the sensingdevice in WO 2004/021944 and an absorbent article may also comprise morethan one such sensor 11. For example, an absorbent article may comprise1-10 such sensors 11.

One non-limiting example of an absorbent article 13 comprising a sensor11 is schematically shown in FIG. 4.

Optionally, the sensor 11 may be packaged or encapsulated accurately,not to be exposed to, e.g. mechanical pressure that may affect theresonant frequency or the magnetoacoustic resonant frequency. Then thesensor 11 may be packaged in a way that the wetness or at least onebiological and/or chemical analyte can penetrate through the packageinto the sensor 11, e.g. via pores, slots or holes, in the packagematerial. Suitable encapsulations include encapsulations in the form oftags such as tags from, e.g. Sensormatic, or a similar product. Theencapsulations are designed or chosen in each case by a person skilledin the art to fit a specific embodiment.

Furthermore, if the sensor 11 does not comprise any wetness sensitivepolymer or detector molecule, the sensor 11 may in one embodiment beencapsulated in an encapsulation together with an absorbing material,e.g. superabsorbent material (SAP). The encapsulation is then designedto allow liquid to penetrate into the encapsulation and the SAP willexert a mechanical pressure on the sensor 11 when absorbing liquid,moisture or humidity. The mechanical pressure correlates to the amountof e.g. liquid absorbed and will completely or partially dampen theoscillations of the sensor 11. A decrease in the magnetoacoustic effectwill be detected when the oscillations are damped, whereby detection ofliquid, moisture or humidity may be determined. WO 2004/021944 is hereinincorporated by reference in its entirety for further details regardingthe encapsulation in this embodiment and how this embodiment works.

Alternatively, if the sensor 11 does not comprise any wetness sensitivepolymer or detector molecule, the sensor 11 may in another embodiment becomprised in an absorbent structure together with a permanent magnet.When the absorbent material of the absorbent structure swells due touptake of a liquid, humidity or moisture, the absorbent material pushesthe permanent magnet closer or away from the sensor 11. This will changethe DC magnetic field on the sensor 11, whereby the magnetoacousticoscillations are affected. WO 2004/021944 is herein incorporated byreference in its entirety for further details regarding theencapsulation in this embodiment and how this embodiment works.

In general terms, the sensor 11 comprises a piece 2, 4 of a film 1 of amagnetoelastic material, which piece 2, 4 has an initial bendingstiffness in a first direction. The piece 2, 4 is provided with at leastone scored line 5 in the first direction of the piece 2, 4. In addition,the piece 2, 4 is bent along at least one of said at least one scoredlines 5 such that it is provided with a lasting bend in a directiontransverse to the first direction. Due to the lasting bend, an enhancedbending stiffness is provided in the first direction of the piece 2, 4.

Thus, while there have been shown and described and pointed outfundamental novel features of the disclosure as applied to preferredembodiments thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devices, methodsteps and products illustrated may be made by those skilled in the art.For example, it is expressly intended that all combinations of thoseelements and/or method steps which perform substantially the samefunction in substantially the same way to achieve the same results arewithin the scope of the disclosure. Moreover, it should be recognizedthat structures and/or elements and/or method steps shown and/ordescribed in connection with any disclosed form or embodiment of thedisclosure may be incorporated in any other disclosed or described orsuggested form or embodiment as a general matter of design choice. It isthe intention, therefore, to be limited only as indicated by the scopeof the claims appended hereto, and equivalents thereof.

1. A method for providing a piece of a film of a magnetoelastic materialhaving an initial bending stiffness with an enhanced bending stiffnessin a first direction, the method comprising the steps of: a. providingsaid piece with at least one scored line in said first direction of saidpiece, and b. bending said piece along at least one of said at least onescored line so as to provide said piece with a lasting bend in adirection transverse to said first direction, whereby an enhancedbending stiffness is provided in said first direction of said piece. 2.The method according to claim 1, wherein said piece is a strip and thatsaid first direction is the longitudinal direction of the strip.
 3. Themethod according to claim 1, wherein said piece is provided with said atleast one scored line by an etching process.
 4. The method according toclaim 1, wherein said piece is bent along at least one of said at leastone scored line by a mould such that the magnetoelastic material is atleast partially plastically deformed at a bottom of the at least onescored line along which the piece is bent.
 5. The method according toclaim 1, wherein said piece in said step of bending is bent so as toprovide said piece with a lasting bend being curve-shaped, wave-shaped,angular, right-angular, V-shaped, L-shaped, U-shaped or S-shaped.
 6. Aproduct comprising a piece of a film of a magnetoelastic material, whichproduct is obtained by a method according to claim
 1. 7. A sensorcomprising a piece of a film of a magnetoelastic material, which piecehas an initial bending stiffness in a first direction, wherein saidpiece is provided with at least one scored line in said first directionof said piece and that said piece is bent along at least one of said atleast one scored line such that said piece is provided with a lastingbend in a direction transverse to said first direction, whereby anenhanced bending stiffness is provided in said first direction of saidpiece.
 8. The sensor according to claim 7, wherein said piece is a stripand that said first direction is the longitudinal direction (y) of saidstrip.
 9. The sensor according to claim 7, wherein said lasting bend iscurve-shaped, wave-shaped, angular, right-angular, V-shaped, L-shaped,U-shaped or S-shaped.
 10. The sensor according to claim 7, wherein saidpiece is coated with a layer of wetness sensitive polymer on one side,which wetness sensitive polymer is selected from the group consisting oflinear and hydrophilic polymers or chemically/physically cross-linkedswellable polymer gels based on polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide and co-polymers thereof, polyurethane,polyamides, starch and derivatives thereof, cellulose and derivativethereof, polysaccharides, proteins, polyacrylonitrile, polyethyleneimine, acrylate based polymers, and mixtures thereof.
 11. The sensoraccording to claim 7, wherein said piece is coated directly orindirectly on one side with at least one detector molecule adapted todetect at least one target biological and/or chemical analyte.
 12. Anabsorbent structure comprising at least one absorbent layer, wherein theabsorbent layer comprises the sensor according to claim
 7. 13. Anabsorbent article, comprising the sensor according to claim
 7. 14. Theabsorbent article according to claim 13, wherein the article comprises2-10 sensors according to claim
 7. 15. A sensoring absorbent systemcomprising a hand held unit, the hand held unit comprising an excitationcoil generating a magnetic field to magnetize said magnetoelasticmaterial wherein the sensoring absorbent system further comprises theabsorbent structure according to claim 12.